A total of 468 seats in the U.S. Congress were up for election on November 6, 2012.

Heading into the election, Democrats controlled the U.S. Senate while Republicans were the majority in the U.S. House. During the presidential election year, partisan dominance of both chambers of the U.S. Congress was at stake. As a result of the election, Democrats increased their majority in the Senate while chipping away at the Republican majority in the House.

U.S. Senate

The 33 Class 1 U.S. Senate seats were up for election. Of those 33 seats, 23 were held by Democrats and 10 by Republican senators. Democrats needed to win 21 seats to retain their majority while the GOP needed to win 14 seats to win back the chamber.

Defeated incumbents

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US Senate Margin of victory

There were a total of 33 seats up for election in 2012. The following table shows the margin of victory for each race winner, which is calculated by examining the percentage difference between the top-two vote getters. If the race was uncontested, the margin of victory is listed as 100%. Some general facts:

Defeated incumbents

No officials have been added to this category yet.

US House Margin of victory

There were a total of 435 seats up for election in 2012. The following table shows the margin of victory for each race winner, which is calculated by examining the percentage difference between the top-two vote getters. If the race was uncontested, the margin of victory is listed as 100%. Some general facts:

30 races (6.9 percent) had a margin of victory of less than 5 percent. Of those 30 races, 18 were Democratic winners while 12 were Republican.

33 races (7.6 percent) had a margin of victory between 5 and 10 percent. Of those 33 races, 15 were Democratic winners while 18 were Republican.

87 races (20 percent) had a margin of victory between 10 and 20 percent. Of those 87 races, 23 were Democratic winners while 64 were Republican.

285 races (65.5 percent) had a margin of victory of greater than 20 percent. Of those 285 races, 145 were Democratic winners while 140 were Republican.

The fewest votes were in Texas' 29th District, with only 95,611 total votes. Incumbent Gene Green (D) faced two third-party candidates in the general election.

The most votes were in Montana, with 479,740 votes cast. Montana has a total population of 998,199 -- which is roughly 250,000 above the average district size in states without single districts. Because Montana has only one district for the whole state, its voters per district is higher than the rest of the country. The average size of each district is 709,000. The second-most votes cast came in Colorado's 2nd District, with 421,580 total votes.

The average margin of victory of all congressional districts was 31.85%, meaning that on average the winner of each race received nearly twice as many votes as the top opponent. Average MOV for Democratic winners was 35.7%, while the average for Republicans was 28.6%.

The average number of votes cast per district was 281,917, yielding an average voter turnout of 39.76%.

Margin of Victory in 2012 United States House of Representatives Elections

1,267 (64.3%) of the country's 1,971 state senate seats are up for re-election in November 2012, and 4,712 (87.05%) of the country's 5,413 state house seats are up for re-election. Altogether, 5,984 (81.0%) of the country's 7,384 state legislative seats will be up for re-election during the presidential election year.

188 ballot questions were certified for spots on 39 statewide ballots in 2012.

Also, 176 of those ballot questions were on the November 6, 2012 ballot in 38 states. A total of 8 elections on statewide ballot measures were scheduled for 2012.

Historically, even-numbered election years feature significantly higher measures than odd-numbered years. In 2010 alone, 184 ballot questions were certified for spots on 38 statewide ballots. In comparison, only 34 ballot measures were on the ballot in 9 states in 2011.

In 2012, veto referendums exploded on the scene. In 2008, 6 veto referendums were on the ballot for voters to decide on. Two years later in the next even-numbered election year, in 2010, only 4 made the ballot. 13 veto referendums appeared on the ballot for 2012. 11 of those measures appeared on the fall election ballot. Referendums in 2012 challenged a variety of legislation including same-sex marriage, medical marijuana and redistricting.

With Legislative referrals, there was a decrease in 2012, with 119 on the ballot, not including advisory questions and automatic ballot referrals. In 2010, there were 134 legislative referrals that were sent to the ballot, leaving 2012 with 15 less referrals. However, in the previous presidential election in 2008, there were only 100 legislative referrals on the ballot, 19 less than 2012.

Ballot initiatives saw a slight increase from 2010, with 50 citizen-initiatives on the ballot, four more than in 2010. However, compared to 2008, 2012's total fell short of that year's by 18.

Also on the ballot were three constitutional convention questions that were automatically referred to the ballot due to provisions in those respective states' constitutions.

August 28

September 18

November 6

Local measures

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As of December 2011, already 41 elections have been scheduled for 2012. In 2011, at least 1,386 local ballot questions appeared on ballots in 11 states. In 2010 an estimated 1,490 questions appeared on ballots.